(1) Field of the Invention
The present invention relates to an improved connection system for a vehicle wheel spokes, particularly applicable to the spoke of a bicycle wheel.
(2) Description of the Related Art
Heretofore, the vast majority of bicycle wheels have been constructed using steel wire spokes with one headed end for connection with the bicycle hub and an opposing end that is directly threaded to accept a spoke nipple that engages the rim. By adjusting the threaded connection between the spoke and the nipple, the overall length of the spoke may be shortened or lengthened to create a balanced pretension in the spokes of the wheel.
Bicycle spokes serve as structural tensile elements where the tension of the spoke is resisted by the hoop compression of the outer rim hoop to create a remarkably efficient wheel structure for handling the loads associated with the operation of the bicycle. The technology of conventional bicycle spokes has remained unchanged for the better part of a century.
Cyclists are continually striving to reduce the weight and increase the efficiency of their bicycle, especially rotating components such as the bicycle wheel. However, the steel spokes of conventional bicycle wheels are quite heavy and add significant weight to the wheel assembly.
In addition to their excessive weight, steel bicycle spokes have poor vibration-damping characteristics and tend to be very efficient at transmitting road vibration to the rider. By transmitting vibration, rather than absorbing it, the conventional steel-spoke bicycle wheel lacks in rider comfort and control.
In attempt to reduce weight, many makers of high-end wheels have resorted to forming their spokes from thinner gage steel wire. This causes the stress in the spoke to increase and makes the wheel more prone to spoke failure due to fatigue. The thinner steel wire has lower tensile stiffness, which can contribute to a reduced side-to-side stiffness of the wheel.
In the last 30 years, great strides have been made in the development of very lightweight materials that also have excellent tensile characteristics. Some of the most attractive of these materials include high-strength fibers, such as carbon fiber, aramid fiber, liquid crystal fiber, PBO fiber and the like. However, when attempting to utilize them as spokes in bicycle wheel construction, these fibrous materials are far more difficult to efficiently couple or terminate than their conventional steel-wire counterparts. In the few cases where these high strength spokes have successfully been utilized in bicycle wheels, their cost and complexity has been very great. This is the primary reason that the vast majority of bicycle wheels are still constructed using steel spokes.
Accordingly, it is an objective of the present invention to overcome the forgoing disadvantages and to provide a coupling or termination connection for a vehicle wheel spoke or tensile element that is strong, lightweight and inexpensive to produce.
An efficient connector coupling or termination should have a tensile strength that approximates the tensile strength of the lightweight tensile element and should not be so heavy as to detract from the weight benefit of these lightweight materials. In addition, cost is always a concern in the bicycle industry. These lightweight materials are often more expensive than the steel wire that they replace. An overly complex or expensive connector would make such a spoke to be cost prohibitive.
It is a further objective of the present invention to provide a construction as aforesaid which reduces cost and provides a wheel that is light in weight and high in strength and reliability.
Further objects and advantages of the present invention will appear hereinbelow.